382 Reports and Proceedings — Royal Mioroscojjical Society. 



The MoLLTJSCA, represented in past time by the persistence of 

 LamelUbranchiata ... ... ... Cambrian to recent. 



Scaphopoda 

 CMtonidce ... 

 Pteropoda ... 

 Prosobranchiata 

 Cephalopoda (in part) 

 Pulmonifera [Zonites and Pupa) 



Cambrian (?) to recent. 

 Silurian to recent. 

 Cretaceous to recent. 

 Cambrian (?) to recent. 

 Ordovician to recent. 

 Coal-measures to recent. 



The Crustacea, represented in past time by persistent forms such 



as the 



Entomostraca — 



Ostracoda ... ... ... ... ... Cambrian to recent. 



Phyllocarida ... ... ... ... ,, ,, 



{Xiphosura) Limulus ... ... ... Silurian to recent. 



The Arachnida. 



Scoi])iomdse {Seo)-pio) Siluiian to present day. 



The Myriopoda Coal-measures to recent. 



The Insecta. 



Neuroptera Coal-measures to recent. 



Orthoptera 



Thysanura 



Homoptera . . . ■ 



Of newer groups the following which have appeared in later 

 geological time may be cited : — 



The Bryozoa ... Carboniferous to recent. 



The .^'cAmofd'ea, or ' Sea-urchins ' ... ,, ,, 



The Gasteropoda ... ... ... ... ,, ,, 



The Decapoda ... ... ... ... ,, ,, 



The Isopoda, etc. ... ... ,, ,, 



If we except such groups as the Crinoids, the Brachiopods, the 

 Nautilidce, the Xiphosura — which evidently attained their greatest 

 maximum in the past, and, although still surviving, are now but 

 a feeble folk — we shall notice that the modern Echinoids, Bryozoa, 

 Mollusca, Lamellibranchiata, Gasteropoda (Siphonostomata and 

 Pulmonifera), the higher Crustacea (Decapoda, Brachyura, and 

 Macrura), the Isopoda, Stomapoda, etc., and our modern Insects, 

 are far in advance of their ' forbears ' in development, and this is 

 especially true of all the chief existing forms of life. 



Just as in the vegetable world our modern flora (with its wealth 

 of flowering plants) is far more highly organised, varied, and 

 beautiful than the vegetation of the past ages of the world, so is 

 the associated fauna of to-day when contrasted with that of the past. 



But, it may be asked, what prospect is there of arriving at the 

 earliest known ancestor from which all these varied forms have 

 been derived ? What help does the geological record afford us ? 

 My duty, as your guide, is to inform you that our increased 

 knowledge of the older rocks has not shown that we are nearer the 

 fulfilment of the young biologist's dream, and the secret of Pandora's 

 Box remains still undiscovered. We have not as yet reached the 

 beginning of life. 



In the oldest Cambrian of North America, Professor C. D. Walcott 

 has shown the presence of some 61 so-called genera and 142 reputed 

 species, embracing Sponges, Corals, Annelids, Graptolites, Echino- 

 derma, Brachiopoda, Mollusca, lowly Crustacea, and Trilobites. 



